Monoclonal antibodies (MAB) have long been considered as magic bullets in immunotherapy of cancer, infection or autoimmune disease etc. However, the first generation of murine antibodies which were used in humans was rather unsuccessful due to human anti-mouse immune responses.
Human antibodies have been mostly either derived from transgenic mice harboring a restricted set of human Ig genes or selected from large artificial antibody libraries using phage display, yeast display or similar recombinant technologies. These strategies have been designed to eliminate any immune reaction against the monoclonal antibody in the human background. Human antibodies can be produced in transgenic animals (e.g. mice) that are capable, upon immunization, of producing human antibodies in the absence of endogenous immunoglobulin production. Transfer of the human germ line immunoglobulin gene array in such germ line transgenic mice result in the production of human antibodies upon antigen challenge (see, e.g., van Dijk, M. A. and van de Winkel, J. G., Curr. Opin. Chem. Biol. 5 (2001) 368-374; Jakobovits, A., et al., Proc. Natl. Acad. Sci. USA 90 (1993) 2551-2555; Jakobovits, A., et al., Nature 362 (1993) 255-258; Bruggemann, M., et al., Year Immunol. 7 (1993) 33-40). Human antibodies can also be produced in phage display libraries (Hoogenboom, H. R. and Winter, G., J. Mol. Biol. 227 (1992) 381-388; Marks, J. D., et al., J. Mol. Biol. 222 (1991) 581-597). The techniques of Cole et al. and Boerner et al. are also available for the preparation of human monoclonal antibodies (Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985); and Boerner, P., et al., J. Immunol. 147 (1991) 86-95). However such transgenic mice are only capable to provide antibodies wih a restricted set of human Ig genes—those which result from the transfected immunoglobulin gene array.
The methodologies based on mice transgenic for human immunoglobulin genes have allowed the generation of antibodies derived from human germ line sequence, which has reportedly reduced the immunogenicity of the resulting antibody drugs compared to murine or mouse-human chimeric antibodies. However, transgenic mouse-derived human antibodies are limited in their diversity, affinities and specificities compared to natural human immune repertoires.
Similarly, a major drawback of phage or yeast display-based combinatorial library approaches is the random pairing of the antibody heavy and light chains. The dissociation of the original antibody heavy and light chain pairing, non-cognate pairing, necessitate the screening of a large number of clones in order to identify heavy and light chain pairs of high affinity. In addition, such non-cognate pairs may display unwanted cross-reactivity to human self-antigens. Finally, the genetic diversity of target-specific antibodies identified by selection and screening of combinatorial libraries is commonly limited due to inherent selection biases.
Traggai, E. et al., Science 304 (2004) 104-107 describe a method for the development of a human immune system in human cord blood cell-transplanted Rag 2−/−γc−/−mice, which can be used as a preclinical model to evaluate responses to vaccines or live infectious pathogens and to pharmacological compounds that target the human immune system. It was shown that reconstituted and subsequently pathogen vaccinated mice can produce tetanus toxoid specific antibody responses at low levels. However, the method of Traggai et al utilized the non-human pseudomonas exotoxin antigen. There is a need for a methodology for production of a human monoclonal antibody in a reconstituted animal wherein, inter alia, the reconstituted animal can produce human antibodies against a human antigen in a high amount.